1. Field of the Invention
The present invention relates to a semiconductor device including a molded IC fixed to a casing, which is adopted to, for example, a pressure sensor apparatus for a vehicle and the like.
2. Related Arts
FIG. 1 illustrates a sensor apparatus having a molded IC 100 fixed to a casing 200. The sensor apparatus is not a prior art, and is a work of the inventor of the present invention. In FIG. 1, the molded IC 100 contains a signal processing IC. External terminals 101a, 101b, and 101c are taken out from the signal processing IC to respectively serve as a power source terminal, a signal terminal, and a ground terminal. The molded IC 100 is retained within the casing 200 made of resin. The casing 200 is provided with three terminals 201a, 201b, and 201c by an insert molding method. Each end of the terminals 201a, 201b, and 201c extends into a connector portion 200a, while the other end of each of the terminals 201a, 201b, and 201c is fixed to the external terminals 101a, 101b, and 101c of the molded IC 100 by welding to get an electrically communicating state therebetween.
In the above-described constitution, provided that the molded IC 100 and the casing 200 are respectively made of resin materials different from each other and therefore they have different thermal expansion coefficients, the change in size of the molded IC 100 due to thermal expansion or thermal contraction in accordance with environmental temperature change is different from that of the casing 200. Therefore, when a pitch L of the external terminals 101a, 101b, and 101c of the molded IC 100 is equal to a pitch of the terminals 201a, 201b, and 201c, excessive stress is applied to respective fixed portions between the external terminals 101a, 101b, and 101c and the terminals 201a, 201b, and 201c due to thermal expansion or thermal contraction, resulting in fatigue failures of the fixed portions.